One injury which may occur in humans is the fracture of the femur. Most commonly, femur fractures are associated with the proximal end of the femur. These types of fractures often result in a fracture of the femoral head from the remaining portion of the femur (known as a “femoral neck fracture”) or a fracture between the neck and shaft (known as an “inter-trochanteric fracture”).
An injury which occurs less often, but is occurring with increasing frequency, is a fracture of the distal end of the femur. As is known, a pair of condyles are located at the distal end of the femur. Distal femur fractures maybe classified into a variety of types with reference to the condyles. In one class, the fracture is between the shaft of the femur and the condyles of the femur (known as a “supracondylar” fracture). In another class of fractures, one or both condyles are fractured from the femur (known as a “condylar” or “intercondylar” fracture). In yet another class of fractures there are multiple fractures, through the supracondylar and intercondylar areas of the femur.
A variety of treatments have evolved for fractures of the distal femur. One common method of treatment is illustrated in FIG. 1A. Illustrated in FIG. 1A is a fracture of the first type, i.e. a fracture of the femur proximal to the condyles with the condyles remaining intact. In accordance with one method of treatment, an exterior plate A is positioned along the exterior of the femur. As illustrated, the plate A has a number of passages there through. Screws B are passed through the plate A into the femur both in the region of the condyles and an area proximal thereto. In accordance with this form of treatment, the plate is used to secure the fractured condyles to the femur.
Other forms of the plate described above are known. For example, the plate may have an angled blade in the form of a “U”-shaped extension (see FIG. 1B), or an outwardly extending screw (see FIG. 1C). This angled blade or screw may be directed into the condyles, and then the other end of the plate affixed to the femur with screws.
The devices illustrated in FIGS. 1A, 1B and 1C (often termed “condylar plates”) have a number of disadvantages. One significant problem is that the portion of the femur distal to the fracture, i.e. the portion including the condyles, may rotate with respect to the device. When the condyles are placed in a position of stress, that portion of the femur rotates both with respect to the device and the remainder of the femur. This prevents healing of the fracture or healing in an unnatural or non-anatomically correct position.
A similar problem exists in the arrangement in FIG. 1C in that the entire screw which engages the condyles may rotate relative to the plate. Thus, even if the condyles do not rotate relative to the screw, that portion of the femur may still rotate or move relative to the remainder via rotation of the screw through the plate.
Another problem is that fixation is often made difficult when the femur is osteoporotic. In the example illustrated in FIGS. 1A, 1B and 1C, osteoporotic bone may not permit secure engagement of the screws or blade.
Yet another problem with fixation devices applied to the surface of the femur is that the plate must endure significant cantilever moments that may cause the plate to break or screws to pull out of the bone. These methods therefore require that the leg be immobilized and no weight borne upon the leg until the fracture has healed. For example, with reference to the prior art method and device illustrated in FIGS. 1A, 1B and 1C, the connection of the plate A and the plate itself is generally insufficient to adequately fix the fracture to permit the femur to bear weight. In fact, the plate and screws generally can not tolerate any significant load bearing at all. This again results in stresses which increase healing time or prevent healing, at least without other measures such as external bracing, immobilization or the like.
An improved method and apparatus for treating distal femur fracture is desired.